Method of preventing blows in manufacture of pneumatic tires



J. F. REHEISER' METHOD OF' PREVENTING BLOWS IN MANUFACTURE OF PNEUMATIC TIRES Flled Aug 24, 1950 Sept. 1, 1953 JNVENTOR .JosEPH F. REI-Imam @Y 6 Patented Sept. l, 1953 .METHOD F PREVENTING BLOWS IN .MANUFACTURE OF PNEUMATIC TIRES Joseph F. Reheiser, Eau Claire, Wis., assigner :to United .States Rubber Company, .New York, N.,Y., a corporation of New Jersey Application August 24, 1950, Serial No. 181,207

1 claim. (o1. 15m-14) This invention relates to a method of making pneumatic tires, and more particularly it relates to a method of providing for escape of air trapped between component parts cfa pneumatic tire in process of assembly, to prevent blowing or separation Aof such component parts.

In conventional practice, pneumatic tires are made by superimposing a plurality of plies of skim-coated -reinforcing fabric on a building drum` to forma tire carcass assembly. The tread portionof the tire andassociated side wall portions, usually formed as a single unit by extrusion, are then superimposed on the carcass assembly. The resulting raw tire band is shaped in toroidal for-m, `usual-1y with the aid of a vacuum shaping box, and then vulcanized under pressure in a mold. It sometimes happens that air be comes entrapped-within `the tire `assembly as the component parts arebeing assembled, either between the various carcass plies or, more frequently, between the outer or top ply and the tread portion. An air pocket is thus formed within the `tire assembly, preventing proper union or adhesion of the vtire parts, and when the tire is subjected to vulcanizing temperature and pressure, such pocket spreads out overa relatively large area forming a ,serious defect known as ka blow Tires containing such blows are of course Worthless and mustbe discarded, ,and such tires therefore represent Considerable wastfge of material, time and labor. 'If the vblow is not discovered and the tire is put into service, the tire is in danger of failing suddenly without warning.

Accordingly, it is a principal object of the present invention to provide a method of preventing entrapment of air pockets within a pneumatic tire assembly.

The invention will be described in detail with reference to the accompanying drawing, wherein Fig. 1 is a fragmentary perspective view of a skim coated reinforcing fabric for building a, tire carcass in the manner of this invention;

Fig. 2 is a fragmentary cross sectional view of a raw tire containing such fabric assembled on a building drum; and

Fig. 3 is a perspective view in transverse cross section of a portion of a completed tire, with parts broken away.

The method of this invention contemplates provision of means for escape of air from between the various component parts of the tire as the tire is being assembled so that no air pockets are trapped therebetween and blows are avoided. It has been found that if the skim-coated fabric comprising one or more of the reinforcing ele- 2 ments of the tire is kprovided on one surface Wit minute channels or'passageways in the fgrmo grooves or corrugations, Y any air included bca tween the tire componentsas they are superirnv posed is .permitted to escape and subsequent blows are eliminated.

Referring to Fig. 1, there is shownthereina length of skim coated tire fabric l0 of the chanacter employed in the present invention. Such fabric is a cord fabric composed of a plurality ,of parallel reinforcing filaments Vor strandsV I I, most commonly textile materials such as Vrayonzor ,c,o t. ton yarns or cords, althoughv wire .is also some.- times used for this purpose. `The reinforcing strands, if made of textile material, are .usually impregnated with a resineflatex mixture to im. prove the adhesion to rubber.

Skim coatings I2 and I3 of vulcanizable rubber carcass stock are calendered onto each side of .the fabric. The upper skim coating I2 is -madesufficiently thin with respectto the textile `elenlents II so that such .elements produce perceptible bulges I4 in the `outer surface of the coating. Thus, there is Iformed a `coating .I2 having .on its surface a series of parallel ridgesld correspond ing to the greatest diameter of :the yarnsorcords I I, and having interposed kdepressions .or grOoY-.es I'5, -corresponding .to thev spaces `intervening .ad--l jacent cords. The surface of .the layer I2 thereby has imparted to lit corrugations perceptible visu- Y ally and by touch. With the usual reinforcing yarns or cords having a diameter within the range yof from 0.02 to 0.033 inch, it is found that skim coatings of carcass stock within the range of from 0.0025 to 0.006 inch give the desired roughened effect; it being understood that the thinner coatings are employed with the smaller cords or yarns.

The skim coating I3 on the other side of the fabric is made relatively thick in order to provide the required amount of rubber stock in the tire carcass and in order to maintain the optimum thickness of rubber between superimposed carcass plies. The coating I3 is made from 0.008 to 0.02 inch thick depending on such variables as the size and type of the tire, and the number of plies in the carcass.

Referring to Fig. 2, the carcass I6 of the tire is built up of a plurality of separate layers or plies, in this case four plies, of the skim coated textile fabric I0 on the surface of the usual cylindrical tire building drum I'I. The first layer of fabric I0 is applied to the drum I'I with the corrugated or ridged surface layer I2 (Fig. 1) facing upwardly, and the next ply is disposed on top of this, also with the corrugated surface layer l2 facing upwardly. The two plies are then pressed or stitched firmly together. Any air that has been included between the two plies in process of assembly is enabled to escape by reason of the fact that the ridged surface of the layer I2 presents continuous escape passageways or channels l5 (Fig. 1) extending across the fabric, along which the air passes out as the plies are pressed together. This process is continued until the desired number of plies, in `this case four plies, have been assembled. It will be understood that the reinforcing fabric I0 is conventionally cut on a bias so that the reinforcing strands therein run at an angle from one side of the carcass to the other, alternate The lateral edges of the carcass assemblyV are wrapped around inextensible bead assemblies I8 in the usual manner.

vA-vulcanizable rubber tread assembly I9 including side wall portions is then applied in the form of a strip of suitable length to the carcass band I6 on the drum I1, and spliced and stitched to cause it to adhere firmly thereto. Again, the ridges on the upper surface layer I2 of the upper ply prevent air from becoming entrapped between the tread assembly and the carcass by permitting the escape of air as vthese parts are pressed together.

The raw tire assembly is removed from the buildingdrum l1, and is shaped in torodal form in the well known manner in a vacuum shaping box (not shown), wherein the usual curing bag (not shown) is inserted in the tire. The tire and curing bag are placed in the usual vulcanizing mold (not shown) wherein fluid pressure isapplied to the interior of the curing bag to cause the tire to conform to the mold under pressure. Heat is applied to the tire internally and externally to vulcanize same, forming the completed tire as shown in Fig. 3.

It has been observed in actual practice of the invention that blows are not formed in the tires assembled by the improved method, and the resulting tires when extensively road tested, have shown the same strength, quality, and wearing characteristics as tires made in the conventional manner. Examination of the interior of the tire shows that the various plies and the tread portion become knitted together firmly during the vulcanization operation and no -voids or traces of the corrugations on the surface of the skim coatings remain.

In some cases it is found sufiicient to employ skim coated fabric reinforcing plies having a ridged upper surface only on the upper reinforcing element; that isthe reinforcing ply immediately below the tread assembly, since it is between the bottom of the tread assembly and the top of the carcass assembly that blows most commonly tend to develop. However, it is preferable that all of the plies in the tire be made in this manner. In this way, only one type of ply need be manufactured, and there are equal quantities of rubber provided between the two vuppermost -plies and the two lowermost plies.

The extra heavy skim coating on the bottom side of the bottom ply gives the interior of the tire l casing adesirable smooth surface.

Having thus described my invention what I claim and desire to protect by Letters Patent is:

A method of making a pneumatic tire compri-sing the steps of providing reinforcing plies by calendering a skim-coating of -Vulcanizable rubber stock onto both sides of a tire fabric composed of parallel textile reinforcing elements,y said textile elements having a diameter within the range of from 0.02 to 0.033 inch, the skimcoating on one side of said fabric being from 0.0025 to 0.006 inch thick sothat said textile elements produce perceptible ridges in the surface of said skim-coating, and the skim-coating on the other side of said fabric being from 0.008 to 0.02 inch, superimposing a plurality of such plies on a tire building drum with said ridged surfaces facing upwardly to form a tire carcass, incorporating inextensible beads in the carcass, superimposing a vulcanized rubber tread and sidewall thereon, and shaping and vulcanizing the assembly.

JOSEPH F. REHEISER.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 790,907 Marks May 30, 1bo5 1,862,492 Mallory June 7, 1'932 2,007,909 state July 9, 1935 2,015,459 Musselman Sept. 24, 1935 2,541,506 cuthbertson et a1. Feb. 1s, 1951Y 

